(a) Field of the Invention
The present invention relates to a supported metallocene catalyst using a metallocene compound having a functional group easy to prepare a supported metallocene catalyst for an olefin polymerization, and an olefin polymerization process using the supported catalyst.
(b) Description of the Related Art
In 1976, a German professor Kaminsky has reported that methylaluminoxane (MAO) compound obtained from partial hydrolysis of trimethylaluminum can be used as a cocatalyst and zirconocenedichloride compound can be used as a catalyst in an olefin polymerization (A. Anderson, J. G. Corde, J. Herwig, W. Kaminsky, A. Merck, R. Mottweiler, J. Pein, H. Sinn, and H. J. Collmer, Angew Chem, Int. Ed. Edgl., 15, 630, 1976).
Afterwards, Exxon has revealed that molecular weight and activity of a produced polymer can be controlled by changing substituents on cyclopentadienyl ligand, and applied for a patent (U.S. Pat. No. 5,324,800) regarding an olefin polymerization using a metallocene compound having various substituents.
The homogeneous olefin polymerization catalyst shows unique polymerization properties that cannot be embodied by the existing Ziegler-Natta catalyst. Namely, a molecular weight distribution of produced polymer is narrow, copolymerization is easy, and a distribution of the second monomer is uniform. For propylene polymerization, stereoselectivity of a polymer can be controlled according to the symmetry of a catalyst. These unique properties made it possible to synthesize a novel polymer that could not be obtained by the existing Ziegler-Natta catalyst and also made it possible to prepare a resin with physical properties required by consumers. For these reasons, said catalyst is actively studied.
In a gas-phase process or a slurry process, a particle shape or apparent density of a polymer should be controlled in order to increase fluidity of polymer and yield of reactor per unit volume, and fouling problem, adhesion of polymer to a wall surface of a reactor, should be removed for continuous operation. In order to solve these problems, a metallocene catalyst should be supported in an appropriate carrier.
Generally, known processes for preparing a supported metallocene catalyst are as follows:
A metallocene compound is physically adsorbed and supported on a carrier, and then contacted with aluminoxane (W. Kaminsky, Makromol. Chen., Rapid Commun. 14, 239 (1993));
Aluminoxane is supported on a carrier and then a metallocene compound is supported thereon (Soga K., Makromol. Chen. Rapid Commn., 13, 221 (1992); U.S. Pat. No. 5,006,600; U.S. Pat. No. 5,086,025);
A metallocene compound is contacted with aluminoxane and then it is supported on a carrier (U.S. Pat. No. 5,240,892).
It is also known that a part of a ligand of a metallocene compound is chemically bonded to a carrier to prepare a supported metallocene catalyst. It is known that, in order to prepare a supported metallocene catalyst, a ligand is attached to a carrier surface through a chemical bond and then a metal is attached to the ligand (K. Soga, H. J. Kim, T. Shiono, Makromol, Rapid Commun. 15, 139 (1994), Japanese Patent Publication Hei 6-56928, U.S. Pat. No. 5,466,766).
It is also known that a metallocene compound having functional groups easy to react with a carrier is firstly prepared and then it is reacted with a carrier to prepare a supported metallocene catalyst. Wherein silicone-based functional groups such as alkoxysilane and halosilane are mainly used (E.P. Laid-open Publication No. 293815, U.S. Pat. No. 5,767,300, E.P. Laid-open Publication No. 839836, Korean Patent Application Nos. 98-12660 and 99-06955). However, these metallocene compounds having silicone-based functional groups are not easy to synthesize and the stability thereof are not good. For examples, E.P. Laid-open Publication No. 839836 describes a metallocene compound having OSiMe3 functional group, but it cannot be commercially used because an yield of the last step for introducing zirconium is unfavorable as 28˜51%.
U.S. Pat. No. 5,814,574 has disclosed a polymerization catalyst supported by binding a metallocene compound having Lewis acid functional groups selected from alkoxy alkyl, heterocycle oxygen radical or alkyl heterocycle oxygen radical to an inorganic carrier. U.S. Pat. No. 5,767,209 has described a preparation of a supported catalyst by binding a metallocene compound having functional groups with Lewis basicity including oxygen, silicone, phosphorous, nitrogen or sulfur to an inorganic carrier in the absence of aluminoxane, and a polymerization process by contacting the catalyst with at least one olefin at pressure and temperature sufficient to cause a polymerization. However, for binding to an inorganic carrier through a functional group with Lewis basicity, a carrier surface must have Lewis acidity. Referring to the Examples of the Patents, in order to give Lewis acidity to the surface of a carrier such as silica, butylmagnesium chloride and TiCl4 are treated or diethylaluminum chloride is treated. In addition, the catalyst bound to the surface through a functional group having Lewis basicity, if activated with a cocatalyst having Lewis acidity such as aluminoxane, is separated from the surface and causes reactor fouling, and a particle shape of a polymer produced therefrom is not good, and thus it is difficult to use in a slurry process or a gas-phase process.